I have in my bike a 1.9" tyre in the front wheel and a 2.2" in the rear. Is it safe to use this tyre sizes?
You can mix and match tire sizes if you want - its relatively common. You just need to make sure that the tires fit on the rim and to a lesser extent are not too thin or too wide for the rim. This is often done for different tire clearances in the front and back, for example.